Mohamed Belaid

Co-digestion of Lawn Grass with Cow Dung and Pig Manure Under Anaerobic Condition

The main objective of this study was to determine optimum biogas production by examining the effect of co-digestion of lawn grass with cow dung and pig manure. In order to conduct this experimental research, each of the substrates was co-digested with lawn grass at varying mixing ratios at stable, thermophilic (45 °C) temperatures, over a retention time of 16 days. Results indicated that co-digesting lawn grass with cow dung and/or pig manure may enhance biogas production and methane content. The results also imply that pig manure may be a more appropriate co-substrate to mix with lawn grass as it indicated a longer biogas potential for a relatively extended period of time, particularly when the lawn grass to pig manure mixing ratio was an even 30:30 g. Cow dung and lawn grass at a mixture 20:40 g had the highest biogas production, bio-methane potential. The C:N ratio, however, seems to be the main contributing factor in biogas yield hence the differences in yield for the different mixtures and substrates. Methane content of biogas was at its lowest levels for mono-digestion of lawn grass. However, mono-digesting lawn grass has a higher bio-methane potential and biogas accumulation over time when compared to a mixing ratio of pig manure:lawn grass of 40:20 g. The best possible bio-methane and biogas production were achieved when lawn grass was co-digested with both pig manure and cow manure at the ratio of, a 15:15:30 g which is attributed to the balanced nutrients and buffering in the digester.

Design Technology for Bioenergy Conversion of Organic Fraction of Municipal Solid Waste

In this study, we investigated the use of a laboratory batch anaerobic digester technology, for biochemical methane potential (BMP) and the bioenergy process design from anaerobic co-digestion of different organics fraction of municipal solid waste (OFMSW) originating from the city’s landfills. The carbon-to-nitrogen (C/N) ratio of OFMSW was found to be below 13. Through co-digestion, the C/N ratio settled at 14. Laboratory experimental data from 500 ml batch anaerobic digester operating at mesophilic temperature of 37 °C and pH of 7 had good productivity of methane of average 59.49% with (54–62%) recommended in the literature and was used to derive volume of digester and surface area. Via the application of the simple multi-attribute rating (SMART) technique of multiple-criteria decision analysis (MCDA) as a decision support tool, the most preferred model option for bioenergy design technology was selected from a list of potential alternatives available in the market. The geometry of the biodigester parameters was comparable with the process.

Solubility of Organics in Triethylene Glycol: Phase Equilibrium Modelling Using the Dortmund and LYNGBY Modified UNIFAC Models

 Abstract—This work is an attempt to predict the solubility of 60 volatile organic compounds (VOCs) in triethylene glycol aimed at thermodynamically testing the suitability of this solvent as an absorbent for the selected organics. The VOC main groups studied were alkanes, alkenes, alkynes, aldehydes, carboxylic acids and alcohols. The Modified UNIFAC Dortmund and Lyngby models were to study the required phase equilibrium as a function of temperature and composition. Triethylene glycol was found to be suitable for the absorption of low molecular weight aldehydes, alcohols and carboxylic acids. Generally, the infinite dilution activity coefficients computed in this study were low (below 100) indicating that the polymeric solvent studied in this work gave favourable phase equilibrium compared to water, the common industrial solvent. The solubility of VOCs was also found to decrease with increase in solute molecular weight. Compared with literature findings, the Dortmund performed better than the Lyngby procedure. However both models failed to accurately predict phase equilibrium behaviour. The authors therefore agree with literature findings that a specialised group interaction needs to be created for this solvent in the UNIFAC models in order to satisfactorily predict activity coefficients for the studied binary interactions.